Ubuntu - removing vCPUs?

[sssstew]

Hi All

Ive got a Ubuntu Linux (64 bit) VM which currently has 2vcpus and i want to reduce this back to 1, anyone done this without issue?

Ive done many windows boxes, but not a ubuntu before, what are the steps?

Thanks

Stewart

[AWo]

The VMware part is easy, just et it to one vCPU.

Depending on the kernel you have (uniprocessor or multiprocessor) you need to change it.

AWo

VCP 3 & 4

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[sssstew]

yeah, vm part is easy. How do i tell what kernel it has? and then how do you change it?

[AWo]

You can see it by using "uname -a". You may have alrady a uniprocessor kernel at hand. If you boot the guest, you may be able to choose it from the boot menu.

AWo

VCP 3 & 4

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[sssstew]

hmm ok it says along the lines of :-

...server #1 SMP Tue Aug 18th......

So i guess the SMP means its symetrical multi processor. Reckon i should just change it in vmware and boot it and see what happens?

[thakala · Accepted solution]

You can simply shut down VM, reconfigure VM to have 1 CPU and reboot, that is all that is required. But please note that 64-bit kernel will always show "SMP" tag even though VM would have only one CPU.

If you wish to get best performance out of your 1 CPU Linux add "divider=10 nosmp noapic nolapic" kernel parameters to grub.conf and reboot, visible difference might not be huge but on heaviliy loaded ESX host VM ready time% will drop quite significantly.

[sssstew]

Perfect, done it now and its fine thanks all